The present invention relates to an electron beam exposure technique used for processing and exposing a semiconductor integrated circuit or the like.
As the packing density of a semiconductor integrated circuit typified by an LSI is becoming higher, a circuit pattern to be formed is rapidly becoming finer. Particularly, it is very difficult to form a pattern of a node of 100 nm or less by an extension of conventional photolithography.
Although electron beam exposure is effective means for forming a micropattern, to apply the technique to a manufacturing site higher throughput is demanded. In recent years, broadly, two methods have been being studied and developed as means for improving the throughput of electron beam exposure. One of the methods is a method of forming a pattern by projecting an electron beam by using a stencil mask. According to the method, although higher throughput can be expected, it is difficult to fabricate the mask, and high cost is estimated.
A second method relates to a method of writing a pattern at once by simultaneously using a plurality of point beams or variable rectangular beams as a conventional electron beam exposure method. In this specification, a method of assigning one electron beam to one electron optical system including an electron lens and a deflector and using a plurality of electron optical systems is defined as a multi-column system, and a method of emitting a plurality of beams to a single electron optical system is defined as a multi-beam system.
An example of the electron beam exposure of the multi-beam system is disclosed in Japanese Patent Application Laid-Open No. 9-245708. An electron beam emitted from a single electron source is condensed to a parallel beam by a condenser lens, and the parallel beam is divided into a plurality of electron beams by an aperture array. From the beams, an intermediate image is formed by a lens array and a deflector array, and the beams are independently emitted by a blanking array. After that, the intermediate image is projected onto a specimen by a projection optical system including a deflector. The system is an innovative system realizing higher resolution and higher throughput since a curvature of field, distortion, or the like which occurs in the projection optical system can be preliminarily corrected by a lens array and a deflector array and it facilitates designing of the projection optical system.
However, according to the multi-beam exposure method, due to a mechanical manufacturing error of the aperture array, lens array, or projection optical system, oblique incidence with respect to an ideal beam center axis caused by the mechanical manufacturing error, or the like associated with the mechanical manufacturing error, intervals of multi-beams may not equal to a predetermined value expected in design. Naturally, variations in beam intervals can be corrected by deflecting the position of each beam by the deflector array. Since an electrostatic deflector of four or more poles which is small is used due to limitation of a space, wiring is difficult, and four or more high-precision analog driving, circuits are necessary per beam. To correct a positional shift of a beam caused by magnification, rotation, or distortion which occurs in association with deflection synchronized with exposure and fluctuations in sample height, a high-speed driving circuit is necessary.
When the number of multi-beams of the multi-beam exposure system is set to 1000 to 4000, the circuit scale becomes large, the number of wires connecting the driving circuit and the deflector array becomes large, and mounting becomes very difficult.
The invention has been achieved in consideration of the problems and its object is to provide a high-precision and high-speed electron beam exposure technique capable of correcting the position of each beam with a simple configuration in a multi-beam exposure system.
To achieve the object, the invention provides an electron beam exposure method for forming a desired pattern onto a specimen by independently emitting and scanning a plurality of electron beams, wherein a deviation between a pattern formed by each of the plurality of electron beams and the desired pattern is controlled by shifting the position of pattern data of the pattern formed by each of the plurality of electron beams.
The invention also provides an electron beam exposure method for forming a desired pattern on a specimen by independently controlling emission and scanning of a plurality of electron beams, including: a step of adding a second region corresponding to a deflection region margin to the periphery of a first region including the desired pattern to be formed by each of the plurality of electron beams, thereby setting a pattern of a third region; a step of obtaining a positional shift amount of pattern data of a pattern formed by each of the plurality of electron beams from pattern data of the desired pattern in the third region; and a step of deflecting each of the plurality of electron beams in accordance with the positional shift amount in the third region.
The invention also provides an electron beam exposure apparatus for forming a desired pattern by independently controlling emission of a plurality of electron beams so as to fall on a specimen via a projection optical system including a deflector, including: a memory for storing pattern data of the desired pattern to be formed by each of the plurality of electron beams; a shift amount computing circuit for computing a positional shift amount of pattern data of a pattern formed by each of the plurality of electron beams from the pattern data of the desired pattern; and deflection control means for deflecting each of the plurality of electron beams in accordance with the positional shift amount.
The invention also provides an electron beam exposure apparatus for forming a desired pattern by independently controlling emission of a plurality of electron beams so as to fall on a specimen via a projection optical system including a deflector, including: a memory for storing pattern data of a third region obtained by adding a second region corresponding to a deflection region margin to the periphery of a first region including the desired pattern to be formed by each of the plurality of electron beams; a shift amount computing circuit for computing a positional shift amount of pattern data of a pattern formed by each of the plurality of electron beams in the third region from the pattern data of the desired pattern; and deflection control means for deflecting each of the plurality of electron beams in accordance with the positional shift amount in the range of the third region.
The positional shift amount of the pattern data includes an amount of correcting variations in intervals of the plurality of electron beams, or an amount of correcting a positional shift of each of the plurality of electron beams, which occurs due to a whole electron optical system including the projection optical system or due to fluctuations in height of the specimen.
The apparatus further includes means for synchronizing computation of the positional shift amount of the pattern and a deflecting operation for exposure with each other.
The means for computing the positional shift amount of the pattern is constructed by means for performing pattern data linear interpolation, and the apparatus includes irradiation amount control means for converting the result of the linear interpolation to an irradiation amount.
The pattern shift amount computing means can set the shift amount by depending on a deflection position for exposure.
The size of the second region for performing the pattern positional shift computation, to be added to the periphery of the first region including the desired pattern to be formed by each of the electron beams is changeable depending on the deflection position for exposure in the memory.